All the members of the intercrine or chemokine family are basic heparin-binding polypeptides which have four cysteine residues which form two disulfide bridges. All these proteins which have been functionally characterized appear to be involved in proinflammatory and/or restorative functions. As such, these molecules are anticipated to have therapeutic potential in bone marrow transplantation and the treatment of infections, cancer, myelopoietic dysfunction, graft versus host disease, and autoimmune diseases.
The chemokine family can be divided into two subfamilies depending upon their amino acid sequence and chromosomal location. The members of the .alpha. subfamily are termed the "C-X-C" subfamily because the first two cysteines are separated by only one amino acid. The human genes in this subfamily include IL-8, GRO/MGSA, and IP-10; murine counterparts include KC and macrophage inflammatory protein 2 (MIP-2). In the chemokine .beta. subfamily, the first two cysteines are in an adjacent position (the "C-C" subfamily). This subfamily includes human MCAF, LD-78, ACT-2, and RANTES. The murine counterparts are JE, TCA-3, MIP-1.alpha., and MIP-1.beta. [J. J. Oppenheim et al, Annu. Rev. Immunol., 9:617-648 (1991)].
The murine KC gene product [Oquendo et al, J. Biol. Chem., 264:4233 (1989)] is induced by platelet-derived growth factor (PDGF) and this is thought to be the murine homolog of the human MGSA/gro.alpha. gene (63.0% amino acid identity to mMIP-2). KC has been expressed in COS-1 cells to show that it encodes a secreted protein [Oquendo, cited above].
Two forms of MIP have been found in cultures of macrophage tumor cells from the mouse: MIP-1 and MIP-2. Murine MIP-2 (mMIP-2) is an inducible protein whose cDNA also has been cloned and sequenced [International Patent Application, Publication No. WO 90/02762 (Mar. 22, 1990)]. Murine MIP-2 has been shown to have potent chemotactic activity for human polymorphonuclear leukocytes (PMN), and to induce PMN degranulation of lysozyme but not of .beta.-glucuronidase [Wolpe et al, J. Exp. Med., 167:570 (1987)]. Further, mMIP-2 has been shown to have myelopoietic enhancing activities for CFU-GM [Broxmeyer et al, J. Exp. Med., 170:1583 (1989)]. The human counterpart of this factor was found to consist of two species, MIP-2.alpha. and MIP-2.beta., also termed gro-.beta. and gro-.gamma., respectively.
The cDNA and amino acid sequences of human gro-.beta. are provided in International Patent Application, Publication No. WO 92/00327 (Jan. 9, 1992); the cDNA and amino acid sequences of human gro-.gamma. are provided in International Patent Application, Publication No. WO 92/00326 (Jan. 9, 1992). Each of these sequences were predicted to encode a 73 amino acid mature protein.
MGSA or gro-.alpha. [Richmond et al, EMBO J., 7:2025 (1988)] is an autocrine growth factor with potent mitogenic activity secreted by human melanoma cells and is the product of the human gro gene [Anisowicz et al, Proc. Natl. Acad. Sci., 84:7188 (1987)].
There remains a need in the art for methods of enhancing the bioactivity of these mature proteins to enable their efficient use as therapeutic or pharmaceutical products, and to minimize the amounts of the proteins necessary to produce a therapeutic effect, thereby lowering toxicity.